Laser cutting of stents has been disclosed in a number of patents including U.S. Pat. Nos. 5,514,154, 5,759,192, 6,131,266 and 6,197,048 and is the preferred technology for stent manufacture in the medical device industry. The conventional approach is to move a hollow tube of metal such as stainless steel under a stationary laser beam. Although the laser is capable of a very rapid cutting speed, the cutting speed of this approach is limited by the speed of the motion drives and in particular the speed of the rotational motor drive.
A typical laser arrangement is shown in FIG. 1. Laser 102 produces a beam 106 which is conditioned as necessary via optical unit 104 and focused into a spot beam which is impinged against hollow tube 108. Hollow tube 108 may be rotated via rotational motor drive 110 and linearly translated via linear motion drive 112.
The conventional laser for cutting is a pulsed Nd:YAG laser which has a pulse duration in the range of approximately 0.1 to 20 milliseconds. This is a long pulse time for cutting and characteristically produces a relatively large melt zone and heat affected zone (HAZ) on the metal. The conventional laser cutting process typically results in the formation of melt dross on the inside edge of the cut tube. This dross must be cleaned off in subsequent processes.
Non-uniformities in the material such as differences in wall thickness create different heat rises in the material and lead to variations in cut quality. Laser parameters have to be re-tuned for optimum cutting for tubes with slightly different wall thicknesses adding to the downtime of the process and reducing the yield.
As the industry moves toward the use of stents having slightly different strut thickness at different positions within the stent, there remains a need for novel methods of rapidly cutting stents from tubes. There also remains a need for developing novel methods of cutting stents from tubes with smaller melt regions and smaller heat affected zone regions than is presently available.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well for the purposes of complying with 37 C.F.R. 1.72.